How do you make a relationship work when the stepson causes all the problems?

My stepsons 10, 11 next week. I've been w/his father for 4 yrs now & we only fight when my ss is around. Anything I say is wrong & if I'm quiet thats wrong. Any suggestions b/c I can't take much more. my ss is always in trouble in school & misbehaves at home constantly. What do I do?